Computer operating system feature for preserving and accessing prior generations of a data set

摘要

A computer operating system method for use with removable computer memories such as optical disks, including write-once disks and write-many disks, for preserving and allowing access to prior generations of a data set, including any kind of data file. When the system is used with a write-many memory, such as a re-writeable CD, the system functions are limited so that generations of the data set older than the currently open generation cannot be revised, even though the physical media would allow revision if the system did not limit this function. To ensure that data written to a write-many disk cannot easily be revised with commonly available software, the data address table for accessing the data is written in a location that is not recognized by available software and is only recognized by software created in accordance with this invention: specifically, the data address table is written in the highest available sector while new versions of the data set are written in the lowest available sector. A user interface function of the operating system is modified to display an identifier for each generation on a removable memory. A user may select any prior generation and read the data in its condition at the time the prior generation was closed.